Sarkozy, in Cannes for the G-20 summit last week, believed he was speaking privately with President Obama when he reportedly described how frustrating he finds Israeli Prime Minister Benjamin Netanyahu. But their microphones were on, and the conversation was picked up by reporters listening to a simultaneous translation.

“I cannot bear Netanyahu, he’s a liar,” Sarkozy told Obama, according to the Reuters news agency, whose reporter was among those who heard the gaffe.

“You're fed up with him, but I have to deal with him even more often than you,” Obama replied, according to a French interpreter.

The Associated Press, which also had a reporter present, said news outlets “did not initially report the [remarks] because they were deemed private under French media traditions.”

It was unclear what prompted Sarkozy to lash out, but the French have made little secret of their frustration with Israel’s decision to expand large-scale settlements. At the United Nations in September, Sarkozy called for Palestinian-Israeli negotiations to begin within a month and for the General Assembly to set a one-year deadline for talks to yield an agreement between Israel and the Palestinians.

The French president is hardly the first world leader to be overheard by reporters in private conversation, and international summits are notoriously unfortunate for them in that regard.

In 1997, then-Canadian Prime Minister Jean Chretien was speaking with other European leaders at a summit in Madrid when he began joking about then-president Bill Clinton, and U.S. politicians in general.

“In your country and my country all the [American] politicians would be in prison because they sell their votes,” he said, before laughing a bit.

“They sell their votes! ‘You want me to vote on NATO, then you have to vote to build me a new bridge in my constituency!' ”

A few days later, Chretien called Clinton and apologized.

View Photo Gallery: Many world leaders have been caught making statements not intended for the public.